When erecting a modern wind turbine it is necessary to lift several heavy wind turbine components to a height being given by the height of a tower of the wind turbine. The respective lifting procedures are typically carried out with special heavy load cranes which may be external cranes or internal (so called built in) cranes. Specifically, after having erected the tower of the wind turbine a nacelle has to be placed on a yaw bearing which is arranged at the top of the tower. Within or at the nacelle there have to be placed in particular an electric generator and in some cases also a main shaft. After having installed the nacelle together with the electric generator and in some cases also the main shaft a hub has to be lifted up and installed to a front end of the electric generator or the main shaft.
For installing the hub firstly the hub has to be lifted up and secondly the hub has to be rotated from a horizontal orientation into a proper at least approximately vertical orientation which allows the hub to be attached to the at least approximately horizontal electric generator or main shaft. Typically, for lifting up the hub a first crane is used and for rotating the hub a second crane with a wire attached to the hub is used. The second crane is used predominantly to control the exact orientation angle of the hub.
EP 2 118 483 B1 discloses a handling unit for moving a wind turbine hub from a transportation position to a wind turbine assembly position. The disclosed handling unit comprises (a) at least one connection point for connection to a wire of a crane system, (b) attachment means for attachment of the handling unit to a structural part of the wind turbine component and (c) an actuating means for actuating the wind turbine component around a rotational center of the handling unit in order to perform a rotation of the (wind turbine) hub. This handling unit has the disadvantage that heavy and from a mechanical point of view relatively complex actuating means are necessary in order to grip the hub in a reliable manner. This causes that the procedure of installing a hub to a nacelle of a wind turbine and also the procedure of dismounting a hub from a nacelle of a wind turbine are at least from a mechanical point of view relatively complex.
There may be a need for facilitating the procedure of installing a hub to a nacelle of a wind turbine and the procedure of dismounting a hub from a nacelle of a wind turbine.